An internal combustion engine may operate in a variety of different modes, particularly in modern engine systems, which are electronically controlled, based upon a variety of monitored engine operating parameters. Some typical operating modes include a cold mode, a warm mode, a cranking mode, a low idle mode, a high idle mode, and an in-between mode which is between the low idle mode and the high idle mode. Various engine operating parameters may be monitored to determine the engine operating mode including engine speed, throttle position, vehicle speed, coolant temperature, and oil temperature, as well as others. In each operating mode it is not uncommon to use different techniques to determine the amount of fuel to deliver to the engine for a fuel delivery cycle. For example, different fuel rate maps might be utilized in two different modes or a fuel rate map might be used in one mode and in another mode an engine speed governor with closed loop control may be used. Electronic control modules that regulate the quantity of fuel that the fuel injector dispenses often include software in the form of maps or multi-dimensional data tables that are used to define optimum fuel system operational parameters. One of these maps is a torque map which uses the actual engine speed signal to produce the maximum allowable fuel quantity signal based on the horsepower and torque characteristics of the engine. Another map is the emissions, or smoke limiter map, which limits the amount of smoke produced by the engine as a function of air manifold pressure or boost pressure, ambient temperature and pressure, and engine speed. The maximum allowable fuel quantity signal produced by the smoke map limits the quantity of fuel based on the quantity of air available to prevent excess smoke.
In many industrial diesel engine applications, the throttle setting indicates the speed at which an operator wants to run the engine, and fuel quantity is varied to maintain the desired engine speed. In contrast, the operator of an otto-cycle engine, such as an automobile engine, typically uses the throttle setting to control fuel quantity, and thereby the speed, of the vehicle being driven by the engine. Currently, many diesel systems use a single full range speed governor whereby the throttle position determines desired engine speed across the operating regime of the engine. This is acceptable for heavy vehicles such as trucks, but is not acceptable for use in automobiles where the throttle, or gas pedal, is used to control fuel quantity to attain the desired vehicle speed. In order to adapt an engine control system originally designed for constant speed engines for use with automobiles, means are required to convert the throttle from a desired engine speed indicator to a desired fuel quantity, or vehicle speed, indicator.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.